I am going to Lisbon on Aug 28th. I have to use American Airlines as I have a voucher with them. But as AA does not fly directly to Lisbon, they have given me three options, each of which allows me to accrue miles with them:

1) TAP JFK to Lisbon (nonstop)
2) Iberia (via Madrid)
3) American Airlines to Heathrow, and then either BA or TAP to Lisbon

The TAP option is the only nonstop flight, so I am considering it, but I haven't heard much about the airline and wanted to know if it is worth trying out. Otherwise I'm quite happy with the AA option: I get a 777, and Heathrow is always fun!

Fly TAP, not only because you have a direct flight, because it's always interesting to try an airline one has never flown before. That would be a great idea, that's what I would do if I were you. I don't think TAP is any worse than an other carrier, you'll like it and like Mirage is pointing out, they have a modern fleet except the A310. From JFK to Lisbon, you'll most likely get an A340. Tap is going all Airbus, their modern equipment includes Airbus A319/A320/A321 and A340 aircraft. Have a nice trip.

If you fly transatlantic with TAP you'll have a good flight and a good service, I'm not so sure about inflight intertainment with TP A340. I'm sure with AA 777 you'll have PTV all way long. But flying with TP is good and cool. In the past AA had offices in Portugal and I presume they wanted to start services to Lisbon after PA left Portugal for good but unfortunetely they never did. Now TWA is over too and we just have Continental as the US flag carrier to USA.
Regards

I would fly with TAP.
I've never flown them on the route JFK-LIS but of course
from LIS to Caracas and back on a A 340 and was quite impressed by
there service. Good inflight-entertainment, comfortable seats, great meals and very nice FA.
I can only recommend TAP!!!!

Have a great trip and enjoy Lisbon, one of the greatest cities I've been to!!!

I would also fly TAP non-stop rather than having the hassle of a transit through LHR. My previous experience with TAP, although not on this sector, was pleasant enough and I particularly enjoy the comfort of the A343.